MTENDELI, Tanzania - Faustin, 34, longs for the idyllic life he enjoyed back home in Burundi. A successful farmer, he grew fruits and vegetables which he sold to sustain his wife and three children.

Mitamba Lukyuku was among the first wave of refugees who fled civil war and political unrest in the Democratic Republic of Congo (DRC) to Tanzania, over a decade ago. “Seven of my family members were ...